title: Molecular consequences of the R453C hypertrophic cardiomyopathy mutation on human β-cardiac myosin motor function.
abstract: Cardiovascular disorders are the leading cause of morbidity and mortality in the developed world, and hypertrophic cardiomyopathy (HCM) is among the most frequently occurring inherited cardiac disorders. HCM is caused by mutations in the genes encoding the fundamental force-generating machinery of the cardiac muscle, including β-cardiac myosin. Here, we present a biomechanical analysis of the HCM-causing mutation, R453C, in the context of human β-cardiac myosin. We found that this mutation causes a ∼30% decrease in the maximum ATPase of the human β-cardiac subfragment 1, the motor domain of myosin, and a similar percent decrease in the in vitro velocity. The major change in the R453C human β-cardiac subfragment 1 is a 50% increase in the intrinsic force of the motor compared with wild type, with no appreciable change in the stroke size, as observed with a dual-beam optical trap. These results predict that the overall force of the ensemble of myosin molecules in the muscle should be higher in the R453C mutant compared with wild type. Loaded in vitro motility assay confirms that the net force in the ensemble is indeed increased. Overall, this study suggests that the R453C mutation should result in a hypercontractile state in the heart muscle.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Ruth F
authors.initials: RF
authors.lastname: Sommese
authors.forename: Jongmin
authors.initials: J
authors.lastname: Sung
authors.forename: Suman
authors.initials: S
authors.lastname: Nag
authors.forename: Shirley
authors.initials: S
authors.lastname: Sutton
authors.forename: John C
authors.initials: JC
authors.lastname: Deacon
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Choe
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Leinwand
authors.forename: Kathleen
authors.initials: K
authors.lastname: Ruppel
authors.forename: James A
authors.initials: JA
authors.lastname: Spudich
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D024722:Cardiac Myosins / Q000235:genetics / Q000378:metabolism*; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002465:Cell Movement; D030342:Genetic Diseases, Inborn / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism; D052898:Optical Tweezers
chemical_list: C501641:MYH7 protein, human; D018994:Myosin Light Chains; D024722:Cardiac Myosins; D018995:Myosin Heavy Chains
keywords: heart disease; optical trapping; single-molecule force measurements